Among various electric contact materials that have been used, particularly Ag—CdO-based materials have excellent electric properties such as deposition resistance, arc resistance and low contact resistance and therefore there has been a large demand for Ag—CdO-based materials in various fields. These materials have been improved over a long time and many academic researches on these materials have been conducted. These materials and manufacturing techniques have reached, so to speak, the maximum.
Recently, however, the cadmium (Cd) discharge standard provision in Japan, EC Directive on Waste from Electrical and Electronic Equipment (WEEE) and the like have been directed toward disuse of Cd, as already known.
Under such conditions, a Cd-free contact material having excellent electric properties that can replace Ag—CdO-based electric contact materials have been increasingly demanded.
Thus, an Ag—(Sn, In, Sb) based internal oxidation contact material has been developed as a medium-load contact having various properties. However, recent devices are miniaturized very rapidly and more strict properties, particularly of a contact, are demanded.
As internal oxidation processing is performed to an alloy formed by adding Sn, In, Sb, Bi or the like to Ag, an internal structure having an oxide precipitated and dispersed therein is provided. However, as a result of research on contact manufacturing conditions, internal oxidation conditions, and damage and exhaustion after contact property evaluation test, it is found that an Ag-rich layer formed on the surface at the time of preparing a contact and an oxide-flocculated layer that is immediately below the Ag-rich layer cause adverse effects such as deposition and increase in temperature of the contact at the time of opening/closing of the contact.
Thus, it is an object of the present invention to solve the problem of disuse of Cd, provide properties equivalent to those of an Ag—CdO-based electric contact material, restrain generation of an Ag-rich layer and an oxide-flocculated layer that is immediately below the Ag-rich layer, which are proper to internal oxidation processing of a Cd-free contact material such as an Ag—(Sn, In, Sb)-based material, and solve various problems such as unevenness in distribution of concentration of added element oxide particles, coarsening of the particles, and flocculation of the particles.